title: Effect of gamma-synuclein silencing on apoptotic pathways in retinal ganglion cells.
abstract: gamma-Synuclein (Syn G) is highly expressed in retinal ganglion cells and the loss of these cells in glaucoma is associated with significant reduction of the intracellular Syn G level. However, a causative relationship between these two events has not been established. Here we show that the knockdown of Syn G results in a decreased viability of the immortalized retinal ganglion cells (RGC-5). The Syn G silencing reduces phosphorylation of serine 112 (Ser112) in Bad protein, a member of the Bcl-2 family that plays a critical role in apoptotic cell death signaling. Our gene expression analysis data suggests that changes in Bad phosphorylation status may be caused by a coordinated shift in activities of kinases controlling Bad phosphorylation and phosphatases catalyzing its dephosphorylation. Moreover, increased phosphorylation of Bad-sequestering protein 14-3-3 detected in these cells is also pro-apoptotic. These results suggest that the homeostatic level of Syn G in RGC-5 cells is required for transcriptional regulation of protein kinases and phosphatases, controlling phosphorylation of Bad and 14-3-3. Lowering Syn G causes Bad dephosphorylation, dissociation from phosphorylated 14-3-3, and translocation to mitochondria where it initiates apoptotic death cascade.
authors.affiliation: Laboratory of Retinal Biology, Veterans Affairs Medical Center, Kansas City, Missouri 64128, USA.
authors.forename: Irina
authors.initials: I
authors.lastname: Surgucheva
authors.forename: Valery I
authors.initials: VI
authors.lastname: Shestopalov
authors.forename: Andrei
authors.initials: A
authors.lastname: Surguchov
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D002470:Cell Survival; D020868:Gene Silencing; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D012165:Retinal Ganglion Cells / Q000378:metabolism*; D051025:bcl-Associated Death Protein / Q000378:metabolism*; D051845:gamma-Synuclein / Q000235:genetics* / Q000502:physiology*
chemical_list: D048948:14-3-3 Proteins; C494821:Bad protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D051025:bcl-Associated Death Protein; D051845:gamma-Synuclein